The present invention relates to a comber having a nipper head with detaching rolls, and having a half lap with a fiber tuft adjacent needles of the half lap.
At a comber during one combing cycle, in other words during a complete forward/backward movement of the nipper, the half-lap with its needles arranged in a segment of a circle accomplishes one complete revolution about its axis. If the comber is operating for example at 300 nips per minute, the half lap will likewise be rotating 300 times a minute and, per rotation, it will comb through the fiber web protruding from the nipper once. In the most inward position, this being the greatest distance of the nipper from the detaching rolls, the needles on the half-lap are at their closest to the nipper. In the most outward position of the nipper, at the shortest distance (detachment length) of the nipper from the detaching roll, the comb cylinder has rotated by about half a rotation, and its needles are positioned on the side turned away from the nipper. To comb the fiber web there is only about one-fifth of the machine cycle available, which means that the sector angle, through which the half-flap carries needles, is determined, and an increase of the combing effect could be achieved only by enlarging the segment radius. Because the comber is required to fulfil certain geometrical conditions in function of the staple length of the fiber material, the radius of the half-lap cannot be enlarged at will, as otherwise these elements would collide.
Persons familiar with the art are aware that only an intimate and multiple contact of the individual fibers with the combing elements lead to a satisfactory combing result, and also that a half-lap carrying needles which gradually become finer will likewise improve the combing result. Accordingly, every effort is to be made to achieve a large surface area for an active half-lap, in order to attain optimum combing quality.
In addition to the performance limitations imposed by the design features referred to above, there is a further disadvantage in that the needle arrangement only passes the brush once per combing cycle, with the result that, at high production rates and in particular with a narrow needle arrangement, the needles cannot be kept sufficiently clean and their effect deteriorates. To avoid this disadvantage, in some cases the machine is periodically switched to a slower speed, which at best incurs loss of production, but more often results in quality fluctuations.